Epitaxial growth and properties of ferromagnetic co-doped TiO2 anatase

We have used oxygen-plasma-assisted molecular-beam epitaxy (OPA-MBE) to grow CoxTi1-xO2 anatase on SrTiO3(001) for x=similar to0.01-0.10, and have measured the structural, compositional, and magnetic properties of the resulting films. Whether epitaxial or polycrystalline, these CoxTi1-xO2 films are ferromagnetic semiconductors at and above room temperature. However, the magnetic and structural properties depend critically on the Co distribution, which varies widely with growth conditions. Co is substitutional in the anatase lattice and in the +2 formal oxidation state in ferromagnetic CoxTi1-xO2. The magnetic properties of OPA-MBE grown material are significantly better than those of analogous pulsed laser deposition-grown material. (C) 2001 American Institute of Physics.